This invention relates broadly to the art of pipe couplings and more specifically to slip-joint pipe couplings that are used for joining plastic pipes abutting one another end-to-end.
Joining the ends of abutting pipes is a common practice in plumbing and there are, of course, numerous couplings used for this purpose. One of the more basic such couplings comprises a cylinder that is slightly larger than the pipe having opposite open ends for receiving the ends of the pipes. The internal surface of the coupling is adhered to the external surfaces of the pipes by an adhesive Normally, such a coupling has an internal annular shoulder approximately in the center thereof to abut against ends of the pipes and thereby ensure that the coupling is properly positioned on, that is centered on, the ends of the pipes, with enough wall extending over both pipes to ensure a proper joint. Such a coupling is shown in U.S. Pat. No. 3,826,521 to Wilhemsen. However, couplings with internal shoulders are not always usable because it is not always possible to bring two pipes together by moving them longitudinally toward each other. For example, where a section of pipe is to be used for joining the ends of two fixed pipes together, the ends of the section cannot be inserted longitudinally into the ends of two such couplings mounted on the two fixed pipes. For this reason, couplings without internal shoulders, also shown in U.S. Pat. No. 3,826,521 to Wilhelmsen, are sometimes used. When this is done the couplings are slid completely onto either the pipe section or the fixed pipes, the section is then placed between the two fixed pipes, adhesive is placed on the ends of the section and the fixed pipes, and the couplings are slid into position over the abutting ends of the pipe section and fixed pipes where the couplings are held until the adhesive cures. A difficulty with this procedure is that personnel performing it do not always draw lines on the pipes or the pipe section indicating where the couplings should be located in order to be centered on abutting ends. Thus, after the adhesive is in place and a worker moves the coupling joints over the abutting ends, he "loses track" of where the abutting ends are positioned and therefore sometimes holds the coupling joint off center, leading to an improper coupling of the section and pipes. It is an object of this invention to provide a slip coupling joint which allows a pipe to be moved laterally to an abutting position with another pipe and thereafter controls the movement of a slip-joint coupling to be slid into a centered position on the abutting pipe ends.
There have been some slip-joint couplings suggested which insure that coupling joints are centered on abutting ends, an example thereof being in U.S. Pat. No. 4,690,434 to Schmidt. Although these devices offer some advantages, they are laterally bulky, that is, requiring an undue amount of space laterally of the pipes. Most such devices include joining bells, or wide mouths, for receiving other coupling joint members which take up undue amounts of space in walls in which they are located. Sometimes such coupling elements actually require that walls be built larger than is necessary for the support of a building. A difficulty with such couplings is that they are not normally streamlined in form, most having stepped outer diameters which makes them somewhat clumsy to use and position among wall framing. Thus, it is an object of this invention to provide a slip-joint coupling which does not take up an undue amount of lateral space, and which is streamlined in form, having only one external diameter when in its final, assembled, configuration.
Further, it is an object of this invention to provide a slip-joint coupling which, when installed, not only has a composite single external diameter but a single internal diameter as well, with the exception of an internal shoulder for contacting the end of one of pipes to be joined.